1. Field of the Invention
The present invention relates to a magnetic head for use in magnetic recording apparatus. More particularly, the present invention relates to a magnetic head for use in a heat-assisted magnetic recording apparatus of magnetically recording information in a state of heating and elevating the temperature of a recording portion of a recording medium by emitting electrons to the recording medium.
2. Description of the Related Art
Magnetic heads for use in the heat-assisted magnetic recording apparatus include those as described in JP-A Nos. 2001-250201 (Patent document D1) and 2001-189002 (Patent document D2).
As the constitutional examples of heat-assisted magnetic recording apparatus, the Patent document D1 discloses an example of providing an electron beam emitting source (emitter cone) near the side of a leading edge from a recording magnetic pole and another example of emitting electrons by roughening the surface of a recording magnetic pole or providing at least one protrusion on the surface of the recording magnetic pole. As the example of the heat-assisted magnetic recording apparatus for recording magnetic information in a state of heating and elevating the temperature of a magnetic recording medium by using a heat source of an optical beam or an electron beam, the Patent document D2 discloses an example of providing a semiconductor light emitting source or an emitter cone on the side of the leading edge of a recording magnetic pole. According to the magnetic recording apparatus, recording can be conducted by elevating the temperature of a magnetic body by electron beams to a curie point or higher and forming magnetic domains by an external magnetic field in the course of cooling.
The patent Documents described above disclose examples of the constitution of providing the emitter cone on the side of the leading edge of the recording magnetic pole. However, in a case of intending to form the emitter cone by the method disclosed in the Patent document D1, it is described as: “it is preferred to define the length of the hole in the direction of the recording track width to about Tw+2 nHe and the length of the hole in the direction of the recording track to about 2 nHe in order to obtain a sharp top end shape causing effective electric field emission assuming, for example the recording track width as Tw and the height of the electron emission source to be prepared as He” (column [0080]). Accordingly, the end face of the leading edge of the recording magnetic pole is spaced from the top end of the emitter cone at least by the distance for the height of the emitter cone. In a specific example of the Patent document D1, the height of the emitter cone is 250 nm (column [0081]). Accordingly, in the constitutional example of Patent document D1, an electron beam irradiation position (that is, temperature increase position) and an application position for recording magnetic line of force on the recording medium are displaced greatly. Further, in a case of intending to provide a plurality of emitter cones in the direction of the recording track, the amount of positional displacement is further increased. In addition, the emitter cone has to be formed by way of complicate steps such as a resist burying step, a thin film forming step, a step of forming a cone-forming hole on a resist, a vapor deposition or sputtering step of an emitter cone material, and a resist removing step. Complicate manufacturing steps lowers the yield and increases the cost, which is not preferred.
On the other hand, in a case of adopting another constitutional example disclosed in the Patent document D1, that is, an example of roughening the surface of the recording magnetic pole or an example of emitting electrons by providing at least one protrusion on the surface of the recording magnetic pole, while the position for electron beam irradiation (that is, position for temperature increase) and a position of applying magnetic line of force for recording on a recording medium can be aligned with each other, since an unevenness is inevitably formed on the surface of the magnetic head in this constitutional example, this may possibly cause occurrence of head crush in a case where the flying height of the magnetic head is in a region from 10 to 20 nm. Further, in a case of roughening the surface of the recording magnetic pole, it is difficult to control the position at the surface of the recording magnetic pole for emitting the electron beams.
In other prior art than the constitutional example of roughening the surface of the recording magnetic pole or the constitutional example of emitting electrons by providing at least one protrusion on the surface of the recording magnetic pole, since magnetic fields leaked from recording bits present on a recording medium or magnetic fields leaked from the recording magnetic pole have a component not in parallel but crossing the flow of electron beams, in a case of not providing a constitution of accelerating electrons to an electron beam emitting device, the electron beams undergo the external force due to magnetic fields to fluctuate the relative positional ratio between the position for electron beam irradiation (that is, position for temperature increase) on the recording medium and the application position of magnetic line of force for recording. Since this means that the position of the recording bits determined by the distribution of the temperature increasing region fluctuates, this causes fluctuation of reading signals on the time axis (jitter) or meandering of the recording track.